What Causes Bipolar Disorder?

The cause of bipolar disorder is not entirely known. Genetic, neurochemical and environmental factors probably interact at many levels to play a role in the onset and progression of bipolar disorder. The current thinking is that this is a predominantly biological disorder that occurs in a specific part of the brain and is due to a malfunction of the neurotransmitters (chemical messengers in the brain). As a biological disorder, it may lie dormant and be activated spontaneously or it may be triggered by stressors in life.

Although, no one is quite sure about the exact causes of bipolar disorder, researchers have found these important clues:

Genetic factors

Bipolar disorder tends to be familial, meaning that it “runs in families.” About half the people with bipolar disorder have a family member with a mood disorder, such as depression.

A person who has one parent with bipolar disorder has a 15 to 25 percent chance of having the condition.

A person who has a non-identical twin with the illness has a 25 percent chance of illness, the same risk as if both parents have bipolar disorder.

A person who has an identical twin (having exactly the same genetic material) with bipolar disorder has an even greater risk of developing the illness about an eightfold greater risk than a nonidentical twin.

Studies of adopted twins (where a child whose biological parent had the illness is raised in an adoptive family untouched by the illness) has helped researchers learn more about the genetic causes vs. environmental and life events causes.

Neurochemical factors

Bipolar disorder is primarily a biological disorder that occurs in a specific area of the brain and is due to the dysfunction of certain neurotransmitters, or chemical messengers, in the brain. These chemicals may involve neurotransmitters like norepinephrine, serotonin and probably many others. As a biological disorder, it may lie dormant and be activated on its own or it may be triggered by external factors such as psychological stress and social circumstances.

Environmental factors

A life event may trigger a mood episode in a person with a genetic disposition for bipolar disorder.

Even without clear genetic factors, altered health habits, alcohol or drug abuse, or hormonal problems can trigger an episode.

Among those at risk for the illness, bipolar disorder is appearing at increasingly early ages. This apparent increase in earlier occurrences may be due to underdiagnosis of the disorder in the past. This change in the age of onset may be a result of social and environmental factors that are not yet understood.

Although substance abuse is not considered a cause of bipolar disorder, it can worsen the illness by interfering with recovery. Use of alcohol or tranquilizers may induce a more severe depressive phase.

Medication-triggered mania

Medications such as antidepressants can trigger a manic episode in people who are susceptible to bipolar disorder. Therefore, a depressive episode must be treated carefully in those people who have had manic episodes. Because a depressive episode can turn into a manic episode when an antidepressant medication is taken, an antimanic drug is also recommended to prevent a manic episode. The antimanic drug creates a “ceiling,” partially protecting the person from antidepressant-induced mania.

Certain other medications can produce a “high” that resembles mania. Appetite suppressants, for example, may trigger increased energy, decreased need for sleep and increased talkativeness. After stopping the medication, however, the person returns to his normal mood.

Substances that can cause a manic-like episode include:

Illicit drugs such as cocaine, “designer drugs” such as Ecstasy and amphetamines.

Nonpsychiatric medications, such as medicine for thyroid problems and corticosteroids like prednisone.

Excessive caffeine (moderate amounts of caffeine are fine).

If a person is vulnerable to bipolar disorder, stress, frequent use of stimulants or alcohol, and lack of sleep may prompt onset of the disorder. Certain medications also may set off a depressive or manic episode. If you have a family history of bipolar disorder, notify your physician so as to help avoid the risk of a medication-induced manic episode.

Last reviewed: By John M. Grohol, Psy.D. on 30 Jan 2013 Published on PsychCentral.com. All rights reserved.